Evaluating Nutrition Recommendations and Identifying Predictors to Promote Healthy Weight Gain through Whole Foods in Athletic Individuals

Athletes from an array of sports and military personnel often desire weight gain, ideally as lean body mass (LBM), to improve performance in sport or military operations. These athletic individuals are commonly encouraged to increase energy intake by ~500 kcal/day with an emphasis on adequate protein and carbohydrate (CHO) and judicious inclusion of healthy fat-containing energy-dense foods (including nuts/nut butters), along with rigorous resistance training (RT). These guidelines target gains of ~0.23 kg/wk (0.5 lb/wk). However, little is known about the efficacy of such regimens, particularly in female athletes. Purpose: 1) to evaluate the outcomes of a 10-wk diet and exercise regimen designed to promote healthy weight gain with excess energy from protein- or CHO-dominant foods, 2) to determine the predictors of weight gain under these conditions, and 3) to survey the methods that athletes currently use to achieve weight gain for athletic purposes. Methods: Two projects included 19 male and 13 female athletes (from a variety of athletic backgrounds with previous RT experience; mean age 25±6 years) who were randomly assigned to receive 500 additional kcal/day above weight maintenance diet through provision of either peanut-based whole foods/snacks (PNT group) or a similar, high-CHO, peanut-free snack (CHO group) along with a supervised RT regimen (60 to 120 min, 3 day/wk targeting major muscle groups). Body composition (via dual-energy x-ray absorptiometry), basic anthropometric measurements, resting metabolic rate, hormonal profile, muscular strength, aerobic fitness (VO2max), and food intake records were assessed at baseline (BSL) and post-intervention with some measurements also assessed at weeks 3 and 7. Predictors of weight gain were determined following the intervention. A third project included an online survey with targeted questions regarding athletes' habits for promoting weight gain. Results: 1) Total body mass (TBM) increased 2.2±1.3 kg with 1.5±1.1 kg as LBM after week 10. The PNT group (n=16; 10 men, 6 women) gained less TBM than the CHO group (n=16; 9 men, 7 women) (1.6±1.1 kg vs 2.7±1.2 kg, respectively, P=0.007) with no differences in LBM (1.2±1.1 kg vs 1.9±1.0 kg, P=0.136). 2) 15 (47% women) of 32 participants gained at least 2.27 kg after 10 weeks with 70% as LBM. Over time, from linear mixed effects models, increased free thyroxine (T4) and increased blood urea nitrogen concentration (as a marker of protein intake) predicted TBM and LBM gains. From general linear models, the CHO energy surplus was a significant predictor of TBM and LBM gains, while the female sex alone was significant for LBM gains at study completion. 3) 168 athletic participants (mean age 24±5 years; 29% female, 71% male) completed the survey and were actively attempting or had attempted weight gain in the last 12 months to gain muscle mass (87.5%), for aesthetic reasons (66.1%), or to improve athletic performance (63.7%). The most prevalent dietary strategies reported to help promote weight gain were consuming more energy than usual (88.0%) from mainly protein foods (83.9%) and using protein powders (67.3). 9.6% of participants reported using anabolic hormones. The main exercise change was increased RT (81.5%). Conclusions: 1) These results suggest that the addition of 500 kcal/day from whole foods/snacks in combination with a rigorous RT program promotes a similar weight gain of ~0.22 kg/week, primarily as LBM, over 10 weeks in both male and female athletes. However, snack macronutrient content may impact the effectiveness of this regimen. 2) Factors that predict ability to gain body weight as expected under these circumstances are incorporating a CHO-dominant energy surplus, consuming overall adequate protein (~1.6 g/kg/day), and free T4 status. Furthermore, athletic women are able to gain LBM as effectively as athletic men. 3) Results confirm that both male and female athletic individuals intentionally attempt to gain weight. Nutrition and exercise professionals may use the findings to be aware of these common dietary and exercise strategies and to better educate their athletic clients on appropriate methods that are evidence-based and not detrimental to health.